Railway track circuit apparatus



M y 1951 P. M. BRANNEN ET AL 2,554,006

RAILWAY TRACK CIRCUIT APPARATUS Filed July 11, 1946 "TE B 56 Cozzzralkd by IMF/w Condz'zi'onm Br 27 Afiflaare Com alled by Traffic Cozzdzkz'onr F 2 INVENTORJ'.

. v PaaZMBzannea mm T H6712 ATTORNEY Patented May 22, 1951 RAILWAY TRACK CIRCUIT APPARATUS Paul M. Brannen and William L. Konrad, Pittsburgh, Pa., assignors to The Union Switch & Signal Company, SWissvale, Pa., a corporation of Pennsylvania Applicatio Ii'July 11, 1946, Serial No. 682,749

7 Claims. (Cl. 246-34) ing at .a frequency necessary to create the desired code. Code transmitters having moving contacts entail the problem of wearand replacement of the contacts.

Accordingly, a feature of our invention is the provision of railway track circuit apparatus incorporating improved code transmitters having no moving contacts.

Another feature of our invention is the provision of improved railway track circuit apparatus using a relaxation oscillator as a code transmitter. Again, a, feature of our invention is the .provision of'track circuit'apparatus incorporating novel means for providing coded energy of different code rates. 1

Other features, objectsand advantages of our invention will appear as the specification progresses.

To accomplish the foregoing features, objects and advantages of our invention, we provide means for operating a relaxation oscillator to generate timed impulses of direct current, the ratio of capacitance and resistance of such oscilmitters are based upon moving contacts operatlator being automatically varied by traffic con- I Referring to Fig. 1, the reference characters Iazand lb designate the track rails of a railway and which rails are formed with a track section DE and which section may be one section of asignal system. {:The track section DE is provided with a track circuit which includes a power supply means connected across the rails at one end of the section and a track relay connected across the rails at the opposite end of the section. The power supply means includes a track transformer, an electron tube amplifier, a relaxation oscil- 1ator-,-andasourceof current.

' The track transformer TE is of the usual form having a primary winding IB energized in a manner to be described hereinafter and a secondary winding II connected across the rails at one end of the section DE, a current limiter impedance I2 being preferably interposed in the connection to the rails.

An amplifying tube I3 of any suitable type and here shown as an indirectly heated triode, is provided'with an output or anode circuit which includes the primary winding I 0 of the track transformer TE. The anode circuit is powered from the current source which in the present case is shown as an alternating current supply and a rectifier. The alternating current supply be any convenient type, such as a generator not shown, the terminals being indicated atBX and GK and connected to the input terminals ofa full wave rectifier I4 through a transformer TI- as will be understood by an inspection of the draw ing. Specifically, the anode circuit for the amplifier tube I3 can be traced from the positive output terminal of rectifier I4 through wire l5, primary winding ID of track transformer TE, anode I6 and tube space to cathode ll of tube I3, resistor I8, ground electrodes I9 and 20, and wire 2I to the negative output terminal of the rectifier. Control of the amplifier tube I3 is effected by a relaxation oscillator in a manner to appear shortly.

A relaxation oscillator is here shown to include an ionization type of tube 22 having an anode 23, a cathode 24 and a control electrode 25. The tube 22 is powered from the current source and to form an anode circuit for the tube the anode 23 is connected to the positive terminal of rectifier I4 through a current limiting resistor 26 and a control resistor 21 in series, and the cathode 24 is connected to the negative output terminal of the rectifier through a resistor 28. The control electrode 25 is biased by a battery 29, which is poled so that the control electrode 25 is positive in potential with respect to the cathode 24 by a voltage predetermined by the battery 29. The parts are so proportioned that the direct voltage applied between anode 23 and cathode 24 from the rectifier is effective to fire the tube only when the control electrode 25 is biased by battery 29. That is to say, the maximum voltage applied to the anode 23 from the rectifier is insufficient to fire the tube in the event there is a loss of the bias voltage applied to the control electrode 25; The firing of the tube 22 is governed through capacitors 3B and 3| which are selectively con nected to the anode circuit of tube 22 according to the positionof a traffic controlled selector here shown as a relay H, the arrangement being such that when relay H is picked up closing front contact 32, the capacitor 3| is connected to the anode circuit to be in multiple with the anode to cathode tube space, and when relay H is released closing back contact 33, the capacitor St is connected to the anode circuit to be in multiple with the anode to cathode tube space.

The relay H may be controlled in any of the usual forms in railway signal systems, and as here shown it is controlled by a simple circuit including a contact 8 which is closedin response to one trafiic condition and open in response to a second trafiic condition. With relay H' picked up to connect capacitor 3i to the anode circuit of tube 22, the capacitor 3| is charged through resistor 21 by the direct voltage of the rectifier and when the charge builds up to approximately the full output voltage of the rectifier, the tube 22 is fired and capacitor 3| discharges through the tube. When capacitor 3| discharges, the voltage across the tube is lowered and the tube: is deionized. This action is repeated over and over, the rate at which the tube is recurrently fired and extinguished being predetermined by capacitor 3| and resistor 21. With relay H released and capacitor 36 connected to the anode circuit, the action is the same, except for the rate'of firing the tube. The capacitors 3E] and 3| and the resistor 27 are of a value preselected so that the tube 22 is recurrently fired at a first code rate of, say, 180 times per minute when relay H is picked up in response to a first trafiic condition and the tube 22 isrecurrently fired at a second code rate of, say, 75 times per minute when relay H is released in response to a second traffic condition.

It is understood that these code rates are given by way of illustration, and the invention is not limited thereto, other code rates can be used.

It is to be pointed out that since the value of resistor 2'! and capacitor :30 or 3| as the case may be, determines the rate of recurrent firing of the tube, it is obvious that in place of using a fixed resistor 21 and varying the capacitance by selecting either capacitor 36 or 3|, a fixed capacitor couldbe used and relay H used to vary the por tion of resistor 2'! interposed in the anode circuit and our invention contemplates such a modification of the apparatus.

The resistor 26 is provided in the anode circuit as an aid in limiting the current volume when the tube 22 is fired, however, since resistor 28 also serves to limit the conduction current, the resistor 26 may not be needed.

Control electrode 34 of the amplifier tube 3 is connected to cathode 24 of the gas tube 22 through wire 35. It follows that each time the tube 22 is fired and conduction current flows in resistor 28, the voltage drop created across resistor 28 is applied across the control grid 34 and cathode I! of the amplifier tube, and a corresponding variation occurs in the anode current of the amplifier tube l3.

That is, the current impulse created by the firing of tube 22 is reproduced in the anode circuit of tube 3. Each such variation of the anode current of the amplifier tube induces a corresponding voltage impulse in the secondary winding of transformer TE, and this voltage impulse when applied across the track rails causes a corresponding current impulse to flow in the track circuit.

The current impulse created by the firing of the relaxation tube will be of a given polarity,

. and capacitor 3!.

and likewise the impulse variation of the current in the anode circuit of the amplifier tube will be of a corresponding relative polarity. The voltage impulse induced in the secondary winding of the track transformer will, however, be an impulse having half cycles of alternate polarity. Thus the track circuit current impulse will have half cycles of alternate polarity.

The track relay TR is a quick acting polar relay and its armature 35 will be operated first to its left-hand position and then to its right-hand positionby each impulse of the track circuit current due to the alternate polarity of the half cycles. Thus the rate of operation of the track relayTR/will correspond to the code rate of impulses; created for the relaxation oscillator and in turn correspond to the different trafiic conditions as reflected by the relay H.

It is apparent that the current impulse flowing. in the track circuit can be made to be of a single polarity by omitting the track transformer or by use of a half wave rectifier interposedin. the connection of secondary winding of the track transformer to thetrack rails. In such casesthe track relay TR would preferably be a neutral relay or a biased polar relay.

In- Fig. 2, the apparatus is similar to that of Fig.1 1, except the amplifier tube and track transformer are omitted and the track relay TR| is preferably of the neutral type. That is, the output of the relaxation oscillator is fed directly. to the track circuit. The anode circuit of the tube 22 of Fig. 2 can be traced from the positive out put-terminal of the rectifier l4 through the control resistor 21, a current limiter impedance 31, rail la, track-relay TRl, rail lb, anode 23 and tube space to cathode 24 of tube 22 and resistor 28 to the negative output terminal of'the rectifier. Capacitors 30 and 3| are connected to the anode circuit through contacts of the traffic controlled relay H in a manner similar to that ex plained for Fig. 1, and the capacitor 3| or 30' and resistor 2'! determine the code rate of the recurrent firing of the tube 22.

Thus, when relay H of Fig. 2 is picked up closing front contact 32, the capacitor 3| is charged and when the voltage reaches appr0ximately the full output voltage oi the rectifier, the tube 22- ionizes and capacitor 3| discharges and the tube is deionized, the conduction current fiowing through the tube causing a current impulse to flow in the track circuit. This action is repeated at a rate predetermined by resistor 21 Each such code impulse of current supplied to the track circuit operates track relay TRI so that the track relay is operated at the preselected code rate.

The operation is similar when relay H is released, closing back contact 33 to connect capacitor 3!] to the anode circuit, the code rate of the current impulses supplied to-the track circuit being preselected for this second trafiic condition.

It is apparent that if additional code rates are required to reflect other trafiic conditions, capacitors in addition to capacitors 3!! and 3| can be used with the apparatus of either Fig. 1 or Fig. 2 and the additional capacitor connected to the anode circuit of the oscillator tube through proper trafiic controlled relays.

It is to be pointed out that the fiow of any discharged current from the capacitor through the current source is avoided due to the asymmetrical characteristics of the rectifier M.

Apparatus such as herein disclosed has the advantages of supplying a track circuit current impulse through code transmittingmeans having no moving contacts to wear. Also, different codes to reflect different traffic conditions are readily obtained by proper selection of the resistance and capacitance of the relaxation oscillator.

Although we have herein shown and described but two forms of railway track circuit apparatus embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appendedclairns without departing from the spirit and scope ode of said tube for firing the tube, a plurality of capacitors of different values, a traffic controlled selector operable to different positions according to different traffic conditions, means including contacts of said selector to selectively connect said capacitors to said anode circuit in multiple with the anode to cathode tube space to recurrently fire the tube at a code rate predetermined by the value of the capacitor connected, and means including a transformer to couple said anode circuit to the track rails of said track circuit to supply to the track circuit current impulses in step with the firing of the tube with each such current impulse having half cycles of alternate polarity to operate said polar track relay at a code rate preselected for each of said traffic conditions.

2. In a track circuit having a code following polar track relay and a power source, a gas filled tube, an anode-cathode circuit including a resistor to connect said power source to an anode and cathode of said tube for firing the tube, a plurality of capacitors of different values, a traffic controlled selector operable to different positions according to different traffic conditions,

means including contacts of said selector to selectively connect said capacitors to said anode circuit in multiple with the anode to cathode tube space to recurrently fire the tube at a code rate predetermined by the value of the capacitor connected, an amplifier tube having an anode circuit connected to said power source and a control grid connected to said anode-cathode circuit of said gas tube" to cause current variations in the anode circuit of the amplifier tube in step with the recurrent firing of the gas tube, and a track transformer having a primary winding interposed in the anode circuit of the amplifier tube and a secondary winding connected across the rails of the track circuit to supply to the track circuit current impulses in step with the firing of the gas tube with each such current impulse having half cycles of alternate polarity to operate said polar track relay at a different code rate for each of said traffic conditions.

3. In a track circuit having a code following track relay and a power source, a gas filled tube, an anode circuit including a resistor and the track rails of the track circuit to connect said power source to an anode and cathode of said tube for firing the tube, a-plurality of capacitors of different values, a traffic controlled relay operable to different positions, means including contacts of said traffic controlled relay to selectively connect said capacitors across said anode and cathode to recurrently fire the tube at a code rate predetermined by the capacitor connected to supply to the track circuit current impulses for operating said track relay at a different'code rate for each of said different relay positions.

&. In a track circuit having a code following track relay and a power source; a gas filled tube having an anode, a cathode and a control electrode; said power source comprising a source of alternating current and a rectifier to supply a direct voltage of a given value, an anode circuit including a resistor and the track rails of saidtrack circuit to connect the output terminals of said rectifier to said anode and cathode, said given direct voltage being ineffective to fire the tube,

- a bias voltage source connected to said control electrode and cathode to bias the control electrode positive in potential with respect to the cathode to render said given direct voltage effective to fire the tube, a capacitor connected at times to said anode circuit in multiple with the anode to cathode tube space to recurrently fire the tube at a preselected code rate, and said track relay operated at said code rate due to the recurrent current impulses thus caused to flow in the track circuit.

5. In a track circuit having a code following track relay and a power source, a gas tube, an anode circuit including the track rails of said track circuit to connect the power source to an anode and cathode of said tube for firing the tube, resistance interposed in said anode circuit, capacitance having connection to said anode circuit to be in multiple with the anode to cathode tube space of said tube to recurrently fire the tube at a rate predetermined by the ratio of the values of said resistance and capacitance, at traffic controlled relay operable to different positions in response to different trafiic conditions, means including contacts of said relay to vary the ratio of the values of said resistance and capacitance to recurrently fire the tube at different code rates in response to the different traffic conditions, and said track relay selectively operated at said different code rates by the current impulses thus caused to flow in said track circuit due to such recurrent firing of said tube.

6. In a track circuit for a track section having a code following relay connected to the rails at one end of the section and a power source of current and a code transmitter having connections to the rails at the other end of the section, the combination comprising; an ionization type of electron tube having an anode, a cathode and a control electrode; an anode circuit including a resistor to connect said power source to said anode and cathode but normally ineffective to fire the tube, another source independent of said. power source connected to said controlelectrode and cathode to bias the control electrode positive in potential with respect to the cathode to condition the tube to be fired by said power source, a plurality of capacitors of different values, a trafiic controlled selector operable to different positions according to different traflic conditions, means including contacts of said selector to connect a different one of said capacitors for each of said different traffic conditions to said anode and cathode to recurrently fire the tube at a code rate predetermined by the capacitor, and said anode circuit coupled to the track rails to supply to the track circuit current pulses in step with the recurrent firing of the tube to operate the track relay at a different code rate for each of said traffic conditions and each of which code rates is stabilized by said bias source.

7. In a track circuit for a track section, the combination comprising, a code following track relay connected across the rails at one end of said section, a power source of direct current; a gas tube having an anode, a cathode and a control electrode; a resistor, said power source and resistor in series connected across said anode and cathode but ineffective to fire the tube, a battery independent of said power source connected across said control electrode and cathode to bias the control electrode positive in potential with respect to the cathode to condition the tube to be fired by said power source, a plurality of capacitors of different Values, a traffic controlled selector operable to difierent positions according to different trafiic conditions, circuit means controlled by said selector to connect a different one of said capacitors for each of said trafiic conditions to said anode and cathode to cause predetermined by the capacitor and said resistor,

8 and said anode and cathode having, connections to the rails at the other end of said section to supply, to the track circuit current impulses of a code rate corresponding to the code rate at which the tube is fired and which code rate is stabilized by said bias battery.

PAUL M. BRANNEN.

WILLIAM L. KONRAD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,629,866 Grondahl et a1 May 2 1, 19.27 1,777,651 Peter Oct. 7, 1930 2,098,040 Hoppe Nov. 2, 1937 2,172,050 Mayberry Sept. 5, 1939 Finch 1 Mar. 2, 1943 

